Fusible plug for steam boilers



Aug. 15, Q LOVEK|N FUSIBLE PLUG FOR STEAM BOILERS Filed June 10, 1930 2 Sheets-Sheet l Mm x w Aug. 15, L D V K N 1,922,625

FUSIBLE PLUG FOB STEAM BOILERS Filed June 10, 1930 2 Sheets-Sheet 2 Patented Aug. 15, 1933 1,922,625 FUSIBLE PLUG FOR STEAM BOILERS Luther D. Lovekin, Villa Nova, Pa.

Application June 10, 1930.

v 10 Claims.

My invention relates to a fusible plug for insertion in the crown sheet-or the like or in the tubes of boilers, usually as a low water safety blow-off, one end of the plug being presented into the interior of a boiler and the other into the furnace heating the boiler.

A purpose of my invention is to provide a fusible plug of the character indicated that is easy and inexpensive to manufacture and well suited to the needs of service.

A further purpose is to protect the fire end of the fusible core of a plug of the character indicated with a packing adapted to prevent contact between the hot furnace gases and the'end surface of the fusible core and toblow out ahead of the core when the core fuses with boiler pressure back of the core.

A further purpose is to shield the end of the fusible core that is presented to the interior of a boiler from contact with the water of the boiler by means of an impervious coating nonreactive with the water of the boiler and desirably of metal, such as copper, tin, nickel, Monel 'metal or the like applied by blow-pipe, electrolytically, or as thin sheets, insufficiently strong to withstand the steam pressure unless supported againstrupture by the fuse element.

A further purpose is to provide a composite fuse plug of the character indicated with an outer non-fusible body well suited to mount the fusible core, a protective packing at the fire end of the fusible core and a metallic sheet at the water end thereof.

, Further purposes will appear in the specification and in the claims.

I have elected to illustrate a few only of the many difierent forms of my invention, selecting forms that are practical and efficient in operation and which well illustrate the principles in- 40 volved.

Figure 1 is a fragmentary vertical section showing a plug embodying one form of my invention.

Figures 2 to 8 are fragmentary views corresponding generally to Figure 1 but showing different forms. I

Like numerals refer to like parts in all figures.

In the past fusibleplugs of the character indicated have sometimes failed to operate because of chemical or physical changes in the fusible material, changes that have unduly raised the fusing temperatures.

It has been found that these changes have been sometimesin ident to the hot furnace gases engaging the fusible core at its lower end, sometimes to engagement between the upper end of the Serial No. 460,164

fusible core and water within the boiler, and sometimes to both of these factors.

A purpose of my invention is to avoid danger of the plug not operating from either or both of these causes.

I protect the lower end of the plug that is presented toward the fire with a packing, desirably of sheet asbestos 01' the like, that is unable to hold its place within the non-fusible body of the plug against the boiler pressure coming against it when the fuse element of the plug melts but does provide the fuse element with sufficient protection from the hot gases within the furnace to avoid any danger of a deleterious chemical or physical reaction between the fuse material of the plug and the hot gases within the furnace.

I also provide a thin metal seal, desirably of copper, tin, nickel, Monel metal or the like, be-

tween the water within the boiler and the upper end of the plug.

In the form shown in Figure l the plug body 19, desirably of brass or the like externally threads at 11 into a crown sheet 12 or the like of any boiler.

The body 10 is perforated longitudinally, an upper portion 13 of the perforation tapering downwardly from the top and a lower portion 14 thereof having a plurality of parallel grooves 15.

I fill the lower or fire end portion of the plug with packing which may comprise sheets of asbestos cardboard 16 fitting the grooves and desirably also the spaces intermediate the grooves.

I place the fusible element 17 in the upwardly flaring portion 13 of the perforation.

While the form shown in Figure 1 provides ample protection from chemical or physical action between the material of the plug and hot gases within the furnace it does not avoid danger of deterioration incident to chemical or physical action between the plug and the water within the boiler.

In Figures 2 to 8 I illustrate different and alternative connections between the non-fusible body 10 and the fusible core 17, showing the same seal 16 of asbestos material or the like at the fire end of the body between the fuse element and the hot gases of the furnace, and also different forms of my metal shield between the fuse element and the water within the boiler.

In Figure 2 the fuse element 17 is an upwardly hollowed truncated cone fitting loosely in the upwardly diverging conical seat 13' presented by the body 10 and presents a circumferential upper surface against the bottom of a thin sheet 18 of copper or the like that is screw clamped circumno longer adequately supported and ruptures under the boiler pressure, which then drives the fuse element and packing into the fire.

In the form shown in Figure 3 a longitudinally hollow fuse element 1'? includes a lower portion threading into the body 10 and an upwardly extending stem that fiares at the top to present a fiat supporting surface against a major portion of the bottom of thesealing --sheet-18 the stem being spaced radially inwardly from the interior of the bore of the body 10 The upward hollowing of the fuse element of Figure 2, and the longitudinal perforation and inward space from the interior of the body of the element-of Figure-3 securesat fusion of the element a desirable instant collapse of the :support .given by the fuse. element to the, sealing sheet and also desirably reduces the quantity, of fuse material for each plug.

In Figured th fuse element lltisadapted to be inserted from the bottom .of the metal body member 10 before the insertion of the packing 1-6 and presents an upwardly extending stem 19 to engage the central portion of the bottom of the sheet metal seal 18 which maybe soldered at 2Q around itsoutside circumference to the plug memberlo The-form shown in Figure 5 is very similar to th hew 1 F r .5 ex p tha h ee metal shield 18 ismou nted in a bushing member 21 being desirably soldered at 20' 'int the up- ,wardly directed counterbore 22 .o'fthe; bushing.

Thebushing 2 1 isthrea ded at 23 into the internally threaded upper end of the {body member 10 packing 24 being desirably provided to prevent'danger of leakage from the; boiler into the interior of the body member.

The form showndn-Figure 6 ,is 1 generally like thatshown in Figure 1 with the exception that-I have provided the top of the body 10 in the upper end of the fuse element l'liwith a metallic coating '18 thatmay be deposited by a blow gun,

electrolytically, or otherwise. 7

The metallic coating should adhere so closely to the metal .ofthe plug body as to insure against leakage of ,the water'into thespace within the body.

The form shown in Figure 7 is generally like that. of Figure 6 except that the plugis inserted from below thecrown seat instead of fromabove The form shown inFigure 8 is like that shown in Figure 6 except that I have provided-adifferentxconnection between the :fusible element 1'7 and; the non-fusible body-10 ,;in that instead ,of upwardly tapering the body I have provided a succession of parallel grooves 25 that-may desirably have ,a diameter slightly greaterthan the corresponding grooves 14 seating the asbestos packing 15 in the lower portion ofthe body.

It will 'be seen that mail the forms Ihave provided an effective shiel d between .the lower end of thefuse elementand the hot gasesjwithin the furnace; that in all the ,formsexcept the first form I have-provided a .metalli sealbetween'the water of theiboiler and the upper end of the fusible element, the illustrated differences being differed with respect to the connection between the plug body and the fuse material, with respect to the connection between the fuse element and sealing plate at the upper end of the fuse element, and with respect to the form of the fuse element.

In Figures 2 to 5 I have illustrated that the fuse element may desirably be hollow; that it may-desirably present an enlargement to the sealing sheet l8; that it may longitudinally interlock with the body near the lower end thereof in threads or parallel grooves, and extend up- .--wa1dly without filling the interior of the body and desirably flare to present adequate support -forthe bottom of the sealing plate.

.Figures, 6,,'7- and 8 illustrate that the metal coating which seals the end of the fusible element from the water of the boiler may comprise merely'a film of metal such as is readily deposited by means of a blow pipe or electrolytically. Inall the. forms :shown the sealing sheet is no longenable-,to withstand the; boiler pressure when the-fusible core fuses, the,boiler,pressure blowing the ,--fused core and packing (out into the fire in the usualway as soon as the fuse,

element collapses, -.usua1 y incident to dangerously. low water in the boiler.

Inviewofmy invention and disclosure variat ons an medificai on .t m et individual whim or particular need will;doubtlessbecome evident to .others skilled in;the;art,-.to obtain all or .part 0f thebenefits of my invention without copyingthe structure shown, and I, therefore, claim all such in so far asthey fall within the -reasonable spirit and scope of my invention.

.ildavling thus described my invention, what I claim as new and desire .to'secure by Letters Patent is: v e

l. Ina fuse plug ,of; the charactcrindicated, ,a non fusible body having alongitudinaLperfforation, packing of heat insulating refractory across the fire end of the perforation, a fusible -core atthe otherendf the perforation having a rigid connection w;ith the body normally supporting it from. movement toward the firev end;

of the 1 perforation, a; sheet. of metal sealing the core from the water ,of theboiler.

2. Anon-fusible body of the eharacter indicated having 1 a longitudinal perforation, a acking-therein-of poor heat-conductivity .at the fire,

thereabove, and a thin metal sheet normally.

supported across the perforation for a portion of the sectional .area thereof ,bythetop of the core andfastened to thebody.

e. Anon-fusiblebod-y of the character indicated having a longitudinal perforation, aback-3 mgv therein,- of poor heat conductivity at the fire end thereof, a fusible core in the perforation vconnectedto-the bodytoward its fire. endand spaced. from'the-bod-y for a portion of itslength ported across the perforation for a portion of the sectional area-thereof-by the'top of the-core and circumferentially clamped to the body.

,5. Anon-fusible'body of the characterlindicated having a 1 longitudinal I perforation, parallel 1 ,thereabove, a thin metal sheet normally sup- 5 .1

grooves at right angles to the axis of the body near the fire end of the perforation, sheets of asbestos or the like across the perforation in the grooves, and a fusible core connected to the interior of the plug above the packing.

6. A non-fusible body of the character indicated having a longitudinal perforation, parallel grooves near the fire end of the perforation,- sheets of asbestos or the like across the perforation in the grooves, a fusible core threaded into the body and extending upwardly from its thread connection with the body and a metal sealing sheet sealing to the body across the perforation and normally supported across the perforation by the top of the core.

7. A non-fusible body of the character indicated having a longitudinal perforation, parallel grooves near the fire end of the perforation, sheets of asbestos or the like across the perforation n the grooves, a fusible core threaded into the body and extending upwardly from its thread connection with the body and a metal sealing sheet sealing to the body across the perforation and normally supported across the perforation by the top of the core, said core being hollow for a portion of its length.

8. A non-fusible body having a longitudinal perforation and parallel grooves near the fire end of the perforation and having the water end of the perforation counterbored, packing in the fire end of the perforation, a metal sheet fitting the counterbore and fastened circumferentially to the body sealing the outside of the body from the interior bore and a fusible element intermediate the body and packing, connected to and supported by the body, the said sheet being normally supported by the upper end of the core to an extent adequate to prevent rupture incident to the boiler pressure and the sheet being too weak to prevent rupture when the core collapses in fusion.

9. A body having a longitudinal perforation and parallel grooves at intervals along the perforation, packing in the fire end of the perforation, a fusible element in the water end of the perforation and a metal coating deposited on the top of the fusible element and of the plug body.

10. A fusible plug element adapted for use in Water pressure locations exposed also to fire, comprising a hollow threaded member having the threaded end adapted for exposure to the heat, a heat insulation filling the end of the plug at the threaded end, a fusible member in the opposite end of the hollow member and a film protection for the fusible element.

LUTHER D. LOVEKIN. 

